In the field of high-speed optical communications using optical fibers, optical transceivers are used as a device which converts electrical signals and optical signals into each other. Specifications (shape, dimension, pin assignment, etc.) of pluggable optical transceivers are standardized by Multi Source Agreements (MSAs) specified by employers' organizations of optical transceivers. With such pluggable optical transceivers, an optical module including an optical-electric-conversion element and a circuit board is removably plugged into a cage which is placed on a main board of the communication-equipment side (the host side). When the optical module is plugged into the cage, the circuit board in the optical module is electrically and mechanically connected to an electrical interface connector in the cage. This enables the optical-electric-conversion element or the circuit board in the optical module to convert the following signals into each other: the optical signals transmitted by the optical fiber; and the electrical signals processed by the main board of the communication-equipment side.
Patent Literature 1 describes an optical module in which the alignment of optical axes thereof is adjusted by inserting a locating pin into a board on which a locating hole is formed.